1. Field of the Invention
The present invention relates to a divisional step dot printing device for a wire dot printer. The device according to the present invention can be used for a wire dot type serial printer used, for example, in an electronic computer system.
2. Description of the Related Arts
In a prior art method of divisional step dot printing with a wire dot printer, all of the dot pins are divided into a plurality of groups each consisting of a plurality of successive dot pins, and a first group of dot pins is driven in a first divisional step during a first travel of a carriage over the length of a platen, the next group of dot pins is driven in the next divisional step during the next travel of the carriage over the length of the platen, and the succeeding group of dot pins is driven in the next divisional step during the next travel of the carriage over the length of the platen.
In this method, one row of printing is constituted by a plurality of parts thereof, and the printing of this plurality of parts is carried out sequentially to print one row.
In this method, however, a problem arises in that the paper to be printed and placed on the platen is deformed in different ways during the sequence of the divisional printing steps, leading to an undesirable shifting of the paper, and accordingly, the colors printed by the sequence of divisional printing steps are overlapped or separated from each other.
In another prior art method of divisional step dot printing with a wire dot printer, all of the dot pins are divided into a plurality of groups each consisting of a plurality of dot pins, at intervals of two dot pin positions, and a first group is driven in the first divisional step during the first travel of a carriage over the length of a platen, the next group is driven in the next divisional step during the next travel of a carriage over the length of a platen, and the succeeding group is driven in the next divisional step during the next travel of the carriage over the length of the platen.
In this method, one row of printing is constituted by a plurality of row constituents, and the printing of this plurality of row constituents are carried out sequentially to accomplish the printing of one row.
In this method, however, a problem arises in that the space between adjacent and simultaneously driven dot pins is relatively large, and therefore, the impact of a dot pin on the paper on the platen is made only by a single dot pin, without considering the accumulated effect of the simultaneous impact of a plurality of adjacent dot pins, and accordingly, the density of the colors printed by the sequence of divisional printing steps is usually low.